Deepwater Horizon spill: Sparkling waters hide some lasting harm from 2010 oil spill

New Orleans: Ten years after a well blew wild under a BP platform in the Gulf of Mexico, killing 11 men and touching off the nation's worst offshore oil spill, gulf waters sparkle in the sunlight, its fish are safe to eat, and thick, black oil no longer visibly stains the beaches and estuaries. Brown pelicans, a symbol of the spill's ecological damage because so many dived after fish and came up coated with oil, are doing well.

But scientists who spent the decade studying the Deepwater Horizon spill still worry about its effects on dolphins, whales, sea turtles, small fish vital to the food chain, and ancient corals in the cold, dark depths.

The gulf's ecosystem is so complex and interconnected that it's impossible to take any single part as a measure of its overall health, said Rita Colwell, who has led the Gulf of Mexico Research Initiative.

BP put up $500 million for the independent GoMRI program soon after the spill, part of more than $69 billion it says it has spent overall, including spill response, cleanup, settlements, restoration and other costs.

Some scientists say the recovery has been remarkable since those dark spring days in 2010, when oil billowing from the sea floor began killing wildlife and blackening marshes and beaches from Texas to Florida.

Ed Overton, a Louisiana State University chemist who has studied oil dispersal since the 1970s, said today's visitors to Louisiana's marshes would have to know just where to look to find damage: "So there's still oil there 10 years later. Is it significant compared to what we saw in 2010? And the answer is not only no, but hell no."

Lung disease and other ailments caused by the spill killed more than 1,000 bottlenose dolphins over several years, many of them in Louisiana's hard-hit Barataria Bay, the National Oceanic and Atmospheric Administration reported. More than one-fifth were aborted, stillborn or died soon after birth.

In this July 31, 2010 file photo, a dolphin is seen swimming through an oil sheen from the Deepwater Horizon oil spill off East Grand Terre Island, where the Gulf of Mexico meets Barataria Bay, on the Louisiana coast.

The oil turned tall marsh grass as black as cinders and sank into the muck across Louisiana's coastal marshes, a nursery for an array of birds and fish. "Once all the roots and so on disintegrate, the whole marsh surface, all the soil, is lost. Given the fact that there is rapid sea-level rise and the land is sinking, it's almost impossible to recover," said marine scientist Boesch. Oiled marsh shorelines that weren't lost immediately were more likely to wash away later.

In this April 18, 2013 file photo, water is seen eroding marsh grass on a remnant of Cat Island, which was directly impacted by oil from the Deepwater Horizon oil spill, in Barataria Bay in Plaquemines Parish, La

But the insects worry Louisiana State University researcher Linda Hooper-Bui. She found that most insect and spider species were back to 68% to 72% of pre-spill populations by 2016, and she was expecting to tell a story of insect recovery on the 10th anniversary.

Then her funding dried up, but in August 2019, she collected one last round of samples and found surprisingly few insects. ``Something is going on right now, and it's deeply affected," she said, but she can't tell what caused it.

Far below the surface, deep-sea corals can live hundreds of years, creating habitats for multitudes of creatures near the bottom of the food web. Because of the BP spill, we also know how they can die. Swaths of such coral were killed, and they grow so slowly _ only a few millimeters a year _ that it's hard to imagine how they could be replaced, Boesch said. Researchers found that seven years later, affected but surviving coral were less healthy than unoiled reefs.

Scientists plan to study these deep habitats more extensively, including mapping the gulf's seafloor. To protect the fragile corals, money is being spent to develop techniques for growing and transplanting corals and installing buoys in some places to alert trawlers to the corals' underwater presence.

In this April 19, 2015 file photo, two great egrets mate in their nest in the mangroves on an island in Cat Bay, in Plaquemines Parish, La.